Cleaning steel surfaces



r52. cowosmows. Cross Reference Examiner l 4 iatente cl Apr. 6, 1943 at Drawi This inven ion relates tothe: cleaning of iron and steel surfaces especially-to prepare such suriaoes for subsequent electroplatingic,

.The removal ofoxides, such' asscale: or rust.

nge Application September28; I939; a Serial No. 296,973.,:.

we e w ar ei ii tion containing sulfocyanide ions, any soluble sul' focyanide may be used, for example, ammonium sulfocyanide (NHACNS) orthe sulfocyanide of som, p assiurn, calcium, barium, or strontium.

from irononsteel surfaces priorto electroplat 5 I prefer, however, to use-an alkali'm'etalsulfoing is commonly done'by pickling operations',ifor

example with sulfuric acid. Various other cleam.

ing solutions also are used, such as cyanide-wlotions,- caustic solutions, soaps; and the likes-toremove various foreign matter in addition to-oxide scale from the surface of the steel, In some processes;'several different cleaning operations are combined in order to obtain completerernoval of; difierent kindsof foreign matter; I; w. I haye devised sin-improved method for. cleaning steel and iron surfaces, an object Of'WhiCh is'to clean iron and steel having oxide or other ,i'oreigu matter. thereon. sot-as to produce clean bright surfaces suitable for subsequent-electro- .pla ting. Allurther object, or my invention. is to clean the surface of iron'or steel-wirewhich' has onits surfaceli m e or. other rawing compound in additionto oxide: scale-'o'rrus Other ob iects of my invention willbeapparent from-the following description. .In accordance with the present invention iron or steel surfaces to be cleanedare first given fan'anodic treatment inan aqueous solution of sulfocyanide and are their treated in an acid solutionwhich is capable of; dissolvingiron oxide. Preferablyith'e'acidtreatmefiiskl'ctrolyticitfie surface to be cleaned being.the-anode;- However, a

dic electrolytic treatment also. may

minimum. ac:

cl produces 51s., In practicing my inventionthe anodic I ment in. the suliocyanide solution effects: complete separation iofialt oxide scale and other forteign material from; the surface of the steel but usually;leaves a dark deposit on the surface. The acid treatment completes the cleaning operation, removing the dark deposit left by -the sulfocyes nide solution and producing a clean, bright sur= face, excellently adapted for. subsequent electro plating. The timeof. treatmentrequired inxboth steps will vary depending upon' the specific-sulfa- .cya deand aoid used; and on othen factors. such as temperature, current density,-. and concentrate tions of the ingredients, as-more fully explained below. In general, the timeoi treatment-insect: step will-be in'the order. of]. to o'minutesz i=1 In thefirststep of my process, that is treat ment inthe sulfocyanide solution, that is, a: solo cyanide" by which term I-m'ean to include ammonium sulfocyanide; In this step" the article to treatedis'made' the anode and a suitable elirectelectric current is" applied. The current density employed is not critical but may be va- "r'iedasdesired. It'is preferable not to use a current density which'is too low, as this will increase m 1 l a of time required ror cmpiete-sepa'ri? up the length 3 1. III I eneraily, a current density of from $0 to 1G0 arriper'es per square foot is suitable but higher current densities iay be used if desired' The ternperatureofthe sulfocyanide solution may be iva; ried from room temperature to the boiling point of the solution; generally, a temperature of about t o G-is preferable; The'pr'eferred concentration of the sullocyanide will vary chieflywith the desired time: treatment and with the Sam'- bllity of the sulfocyan'ldeused." When using am moniurr'f suli'ocyanide or sodium sulfocyanide, I prefer to maintain the sulfocyanide concentration of from 2-to 16' ozsper gallon. H

In the second step ofmy process I use an acid solution which: is capable of dissolving iron oxides'b A"varietjiof-acids may be-used for this purpose either alone orin mixturesjfthereof', for example sulfuric acid;'hydrochlorio acid, nitric acidpci'tric acid and a'cetic-acidI- The action of the various known acidsjon iron oxides is well known and: the -'proper---selection of acidand its concentration irr-t-he solution will be apparent to: the skilled'che'mls'tL' 'rg nerauy prefer rouse a: sulfuric acid solution, the concentration of which may vary from about 5 to 75% by weight of 'HQSOQ; I have obtained the best results. in cleaningsteel surfaces, with a sulfuric acid solution of 40 to 50% concentration: While the acid solution may" be used -rionlectrolytically or as a'ieathcd'ie' electrolytic cleaner, I prefer to. use the acid solutlon as an anodic I electrolytic cleaner at a'relatively high current-density,- for example to 250 amperes per square foot or higher.- While lower' current denslties' may-beiisod', the results at .l'ower'ieurrentl densities 'aresimilar to those obtained without the use of the electric current, namely.- a'considerably longer time is required to effect complete cleaning. Also I have found that generally a brighter surface is obtained by the use of the higher current densitis, the work being. the anode". 'The 'cur-re'nt' density also-will vary when other acids are used. For example, it is impossible to use a high current density with the 'weaker acids, such as acetic acid or citric acid.

base metal by the acid. Acid inhibitors are a well-known class of chemicals which are commonly added to acid pickling solutions for pickling iron or steel. The following typical acid inhibitors are examples of inhibitors which are suitable for use in my process: aldehydes, such as furfural; aldehyde derivatives, such as the condensation products of aldol with alpha naphthylamine; organic sulfides-of the type Rm-cs-srcs-NR;

such as thiuram sulfide; saturated heterocyclic compounds containing at least three different atoms inthe ring, two of the atoms. preferably being .nitrogen and carbon, such as N-(parahydroxy-phenyl) morpholine ch as lauryl pyridinium thiocyanate, mus ar oils, such as allyl isothiocyanate; cinchona bark alkaloids and their derivatives, such as sulfurized quinoidine; thioureas, such as di-orthotolyl thiourea: sulfonated oils, such as ichthyol; thiazoles, such as anilinobenzthiazole; thioglycollic acid and its I on the surface.

of the treatment in sulfocyanide solution, in practicing my process.

My hereindescribed method is especially well adapted for cleaning cold-drawn steel wire to prepare it for electroplating. Such wire usually has on its surface lime or other material used as drawing lubricant and also may have rust spots The removal of the drawing lubricants, such as lime which usually fills small cracks and crevices'on the surface of the wire, is exceedingly diflicult by ordinary means and usually mechanical means, such as brushing or the like, are required to effect its complete remo'val. It is also diflicult to remove the rust spots without undue attack of the underlying steel by the usual pickling processes, especially when such methodsare sufiiciently drastic to remove the derivatives, such as ethyl thioglycollic acid and diphenyl thiohydrantoin; petroleum oil residues and waste acids; extracts from destructive distillation of carbonaceous matter; oil refinery waste;

and pyridine bases...

In one preferred method for practicing my invention, a steel surface to be cleaned is first treated anodically in a sulfocyanide solution containing about 8 ozs. per gallon o r-sodium sulfocyanide o ammon u perature of abo u an anode current density of 60 to 70 amperes per square foot. This anodic treatment is continued for a period of one to two minutes. The steel article then is made the anode in a sulfuric acid solution which contains sulfurized quinoidine or other acid inhibitor. The acid solution is warmed to about 40 to C. and the anode current density is 100 to 250 amperes per square foot. ,The treatment in the acid solution is continued for about one minute. The cleaned article then is water rinsed to remove adhering acid. '11 desired,-the water rinse may be dispensed with, if the adhering acid is not incompatible with the subsequent electroplating operation. After this treatment the steel article will have a bright, clean surface and is ready to be electroplated. I

In the above described anodic treatments, types of cathodes commonly employed in anodic cleaning operations may be used.- For example, cathodes of iron, steel, carbon or lead are suitable for practicing my process.

I ocyanide tatem- I am aware that heretofore it has beenproposed 1. Aprocess for cleaning the surface of a ferrous metal article, which comprises making said article the anode in an electrolyte consisting essentially of a solution containing sulfocyanide ions in concentration equivalent to at least about 2 ounces per gallon of alkali metal sulfocyanide and thereafter contacting said article with an acid solution which is capable of dissolving iron oxides. I

2. The process according to claim 1 in which the said article is made the anode in the said acid solution.

3. A process for cleaning the surface of a ferrous metal article, which comprises making said article the anode in an electrolyte consisting essentially of a solution of an alkali metal sulfocyanide containing at least about 2 ounces per gallon of said sulfocyanide and thereafter making said article the anode in a sulfuric acid solution which is capable of dissolving iron oxides. 1 2 4. A process forcleaning the surface of a ferrous metal article, which comprises making said article the anode in an electrolyte consisting essentially of a solution of an alkali metal sulfocyanide containing at least about 2 ounces per gallon of said sulfocyanide and thereafter making said article the anode in a sulfuric acid solution which is capable of dissolving iron oxides, at an anodic current :density in said acid solution of not less than about amperes per square foot.

'5. A process for cleaning the surface of a ferrous metal article, which comprises making said article the anode in an electrolyte consisting essentially of a solution of ammonium sulfocyanide containing at least about 2 ounces per gallon of said sulfocyanide and thereafter making said article the anode in a sulfuric acid solution which is capableof dissolving iron oxides, at an anodic current density in said 'acid solution of not less than about 100 amper'es per square foot.

6. Aprocess for cleaning the surface of a ferrous metal article, which comprises making said article the anodein an electrolyte consisting essentially of'a solution of sodiumsulfocyanide containing atleast about 2 ounces per gallon of said sulfocyanide and thereafter'making said article the anode in a sulfuric acid solution which is capable of dissolving iron oxides, at an anodic 52 cowo smows l 4 6 current density in said acid solution of not less than about 100 amperes per square foot.

7. A process for cleaning the surface of a ferrous metal article, which comprises making said article the anode in an electrolyte consisting essentially of an electrolyte containing two to sixteen ounces per gallon of an alkali metal sul- Cross Reference focyanide at a temperature of 60 to 80 C. and an anodic current density of 40 to 100 amperes per square foot and thereafter making said article 7 the anode in an electrolyte containing 40 to 50% by weight of sulfuric acid at an anodic current density of 100 to 250 amperes per square foot.

. CHRISTIAN J. WERNLU'N'D.

Examine! 

